JP2007265750A - Fuel cell device and fuel cell assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell device and a fuel cell assembly capable of preventing the generation of cracks or gaps in a seal part of a gas manifold. <P>SOLUTION: One end side in the shaft length direction of a fuel cell 33 formed by surrounding the side face of a supporting substrate 33a with a gas passage 34 formed in the shaft length direction therein by a dense solid electrolyte layer 33c and an interconnector 33f with their ends overlapped each other is covered with a cover layer 42 formed of an inorganic insulating material to cover a step c formed by overlapping the interconnector 33f with the solid electrolyte layer 33c. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell device and a fuel cell assembly in which a dense solid electrolyte layer and an interconnector surround and surround a side surface of a support body in which a gas passage is formed in an axial length direction. Concerning solids.

  In recent years, various types of fuel cell systems such as solid polymer, phosphoric acid, molten carbonate, and solid electrolyte have been proposed as next-generation energy. In particular, the solid oxide fuel cell system has an operating temperature as high as about 700 to 1000 ° C., but has advantages such as high power generation efficiency and the ability to use exhaust heat, and research and development are being promoted.

  In a typical example of a solid oxide fuel cell system, a fuel cell including an elongated plate-like support substrate is arranged in a required direction, and a plate shape that defines the upper surface of the gas manifold on one side, usually the upper surface, of the gas manifold. It is fixed via an appropriate holding member which may be a member. Each support substrate is formed with a gas passage extending through in the longitudinal direction thereof. The gas passage communicates with the gas manifold, and the fuel gas (or oxygen-containing gas) fed into the gas manifold is provided. Gas) is caused to flow from within the gas manifold to each gas passage of the support substrate.

In order to prevent the fuel gas (or oxygen-containing gas) in the gas manifold from leaking from the periphery of the holding member and the support substrate to which one end of the cell is fixed, the one end of the cell is fixed to the holding member with gas tight It is important that Patent Document 1 below discloses a fixing structure in which one end of a cell is fixed to a holding member in a gastight manner.
JP 2005-183376 A

  In the seal part of the fuel cell, a gas tight seal on the air side and the fuel side is required, and the seal part is exposed to an oxygen-containing gas atmosphere containing water vapor and a reducing atmosphere containing water vapor. In addition, the fuel cell has various members such as a fuel electrode layer, a solid electrolyte layer, an oxygen electrode layer, and an interconnector. For example, the dense solid electrolyte layer and the end portions of the interconnector are overlapped with each other. The gas surrounding the support and flowing through the gas passage of the conductive support and the gas flowing outside the cell must be shut off, and the fuel is generated by overlapping the end of the solid electrolyte layer and the end of the interconnector. A step is inevitably generated on the surface of the battery cell.

  The portion where the step of the fuel cell is generated is bonded and fixed to the gas manifold with a seal glass. When there is a step, the fuel cell and the bonding material to the gas manifold are used. Due to the difference in thermal expansion coefficient of a certain seal glass, and due to the difference in shrinkage behavior after heat treatment of the seal glass, the stress generated on the seal part is increased, and defects such as cracks are generated in the seal part. There was a problem that occurred.

  Also, in the firing stage when the sealing glass is poured into the gap between the fuel cell and the gas manifold and bonded and fixed, the sealing glass shrinks with firing and then softens, but the fluidity state after softening In the case where the wettability with the fuel cell or the metal manifold is poor, a gap is formed in the vicinity of these interfaces, and the sealing process must be repeated. When the wettability between the interconnector or the solid electrolyte layer and the seal glass is poor, there is a problem that a gap is generated.

  It is an object of the present invention to provide a fuel cell device and a fuel cell assembly that can prevent generation of cracks and gaps in a seal portion of a gas manifold.

  The fuel cell device of the present invention is a fuel cell comprising a dense solid electrolyte layer and an interconnector surrounding the side surfaces of a support body in which a gas passage is formed in the axial length direction. One end side surface in the axial length direction is covered with a coating layer made of an inorganic insulating material so as to cover a stepped portion where the interconnector and the solid electrolyte layer overlap. The fuel battery cell is characterized by having a power generation unit formed by sandwiching the solid electrolyte layer between electrode layers on the conductive support and the interconnector.

  In the fuel cell assembly of the present invention, one end of the fuel cell device as described above is joined to a gas manifold by a seal glass, and the gas passage of the fuel cell device communicates with the gas manifold. It is characterized by that.

  The interconnector generally protrudes from another member, for example, a solid electrolyte layer, in order to electrically connect the fuel cells, and the end of the interconnector and the solid electrolyte layer is used to shut off gas inside and outside the fuel cell. The parts overlap each other and a step is formed, but the step is eliminated because a part of the step between the interconnector and solid electrolyte layer to be joined to the gas manifold is covered with a coating layer, and thus The fuel cell device with no level difference is joined to the gas manifold by the seal glass. Therefore, the stress concentration based on the stepped portion as in the conventional case does not occur, and thus it is possible to prevent the occurrence of cracks in the cooling process after the heat treatment to join the gas manifold with the seal glass.

  In the fuel cell assembly of the present invention, a part of the coating layer of the fuel cell unit is embedded in the seal glass. In such a fuel cell assembly, one end portion of the fuel cell unit is joined to the gas manifold by a seal glass, but the coating layer is formed longer than the joint portion of the gas manifold. It can be improved.

  In the fuel cell assembly of the present invention, the coating layer is made of a solid electrolyte material or glass. In such a fuel cell assembly, when the coating layer is a solid electrolyte material, the same material as that of the solid electrolyte layer can be used, which is easy to manufacture and there is a problem in the bonding property with the conductive support. It can be formed without generating.

  On the other hand, when the coating layer is made of glass, the stepped portion can be easily coated and sealed by softening and melting during glass firing when the coating layer is formed on the fuel cell.

  Further, when the coating layer is made of a solid electrolyte material or glass, the solid electrolyte material or glass shrinks in the direction of compressing the fuel cell in the cooling step after heat treatment of these materials, thereby preventing the generation of gaps. Further, the wettability with the sealing glass (glass for bonding to the gas manifold) after that can be improved.

  In the present invention, it is desirable that the inorganic insulating material constituting the coating layer has a thermal expansion coefficient intermediate between the seal glass and the fuel battery cell. Thereby, an inclination thermal expansion arrangement | positioning is attained about a fuel cell, a coating layer material, and a seal glass, and generation | occurrence | production of a crack can further be suppressed.

  Further, according to the present invention, it is desirable that the coating layer material is made of an inorganic insulating material having a strength higher than that of the seal glass. Thereby, even when there is a difference between the thermal expansion coefficients of the members constituting the fuel cell and the seal glass, a coating layer material having a strength higher than the stress caused by the thermal expansion difference is formed at one end of the cell. Thus, the stress generated in the low-strength seal glass can be reduced, and as a result, a crack-free seal glass can be formed.

  Further, according to the present invention, by coating one end of the fuel cell in advance with a coating layer, for example, when a glass material is used for the coating layer, the layer coated during firing shrinks, but the cell is compressed. In order to shrink and soften in the direction, a dense coating layer can be provided in one step without a gap between the coating layer and the fuel cell. Furthermore, by providing such a coating layer, since the glass material is the same as the sealing glass, the wettability between the coating layer and the sealing glass is good, and the gap between the fuel cell and the gas manifold can be reduced with a small number of steps. It becomes possible to fill.

  Further, by selecting a highly insulating material as the material of the coating layer, it is possible to ensure insulation between the fuel cells and between the fuel cells and the gas manifold. In particular, since the interconnector is conductive, it is not always necessary to select a highly insulating material for the sealing glass by covering the portion with a coating layer having a high insulating property in advance. That is, a wide range of materials suitable for filling the gap between the fuel battery cell and the gas manifold can be selected for the seal glass.

  In the fuel cell assembly of the present invention, since the stepped portion where the interconnector and the solid electrolyte layer at one end of the fuel cell device joined to the gas manifold overlap with each other is covered with the coating layer, the step is eliminated. In this way, the fuel cell device with no level difference is joined to the gas manifold with the seal glass, so that stress concentration based on the level difference as in the conventional case does not occur, so that the gas manifold is joined to the gas manifold with the seal glass. As a result, it is possible to prevent generation of cracks and gaps in the sealing glass in the cooling step after heat treatment.

  FIG. 1 shows a fuel cell assembly according to the present invention. Reference numeral 31 denotes a storage container having a heat insulating structure. Inside the storage container 31, a cell stack 35 in which a plurality of fuel battery cells 33 are gathered, an oxygen-containing gas supply pipe 39 inserted between the fuel battery cells 33, and heat provided above the cell stack 35. It is comprised from the exchange part 41. FIG. In FIG. 1, the oxygen-containing gas supply pipe 39 is indicated by a broken line for convenience.

  The storage container 31 includes a frame body 31a made of a heat-resistant metal and a heat insulating material 31b provided on the inner surface of the frame body 31a.

  In the cell stack 35, for example, as shown in FIG. 2, a plurality of fuel cells 33 are arranged in two rows, and the electrodes of the two adjacent outermost fuel cell cells 33 are connected by a conductive member 42. Thus, the plurality of fuel cells 33 arranged in two rows are electrically connected in series.

  The fuel cell 33 will be specifically described. As shown in FIG. 3, a porous conductive support (hereinafter referred to as a support substrate) 33a having a plate-like cross section and a plate-like and columnar shape as a whole is shown. A porous fuel side electrode 33b is provided so as to cover the flat one side main surface and both end arc-shaped side surfaces of the support substrate 33a, and further to cover the fuel side electrode 33b. A dense solid electrolyte layer 33c is stacked, and an oxygen side electrode 33d is sequentially stacked on the solid electrolyte layer 33c. An intermediate film 33e, an interconnector 33f, and a current collecting film 33g are sequentially laminated on the flat main surface of the other side of the support substrate 33a opposite to the oxygen side electrode 33d.

  The fuel cell of the present invention has a plate shape and a column shape as a whole, and six gas passages 34 are formed through the support substrate 33a in the axial direction. .

  That is, the fuel cell 33 has a cross-sectional shape including an arc-shaped portion B provided at both ends in the width direction and a pair of flat portions A that connect these arc-shaped portions B. It is flat and formed substantially in parallel. One of the flat portions A of these fuel cells 33 is configured by forming a fuel side electrode 33b, a solid electrolyte layer 33c, and an oxygen side electrode 33d on one main surface of the support substrate 33a, and the other flat portion. A is configured by forming an intermediate film 33e, an interconnector 33f, and a current collecting film 33g on the other main surface of the support substrate 33a.

  The solid electrolyte layer 33c extends from one main surface of the support substrate 33a to the other main surface via the side surfaces on both sides, and both end portions of the interconnector 33f are on both end portions of the solid electrolyte layer 33c. Overlap and form a stepped portion c. In other words, on the side surface of the support substrate 33a in which the gas passage 34 is formed in the axial length direction, the dense solid electrolyte layer 33c and the interconnector 33f surround the end portions thereof. In FIG. 3, the overlapping portions are exaggerated. In FIG. 2, the overlapping portion between the solid electrolyte layer 33c and the interconnector 33f is omitted and simplified.

  A portion where the fuel side electrode 33b, the solid electrolyte layer 33c, and the oxygen side electrode 33d overlap is a power generation unit. This power generation portion may be formed up to the arcuate portion B. In the fuel cell 33, the power generation unit is formed in the flat part A.

  In addition, it is desirable that the arc-shaped portion B has a curved surface in order to relieve the thermal stress generated due to heating and cooling accompanying power generation.

  In addition, it is desirable that the major dimension of the support substrate 33a (the distance between the side surfaces of the support substrate that forms the arc-shaped portion) is 15 to 40 mm, and the minor diameter dimension (the distance between the main surfaces that forms the flat portion) is 1 to 10 mm. In addition, although the shape of the support substrate 33a is expressed as a plate shape, it can also be expressed as an elliptical shape or a flat shape by changing the major axis dimension and the minor axis dimension.

  In addition, a dense solid electrolyte layer and an oxygen-side electrode made of porous conductive ceramics are sequentially laminated on the outer surface of the fuel-side electrode mainly composed of metal, and the outer surface of the fuel-side electrode opposite to the oxygen-side electrode. An interconnector may be formed on the fuel electrode and the fuel side electrode may be used as a support.

  As shown in FIG. 2, an elastic current collecting member 43 made of metal felt or a metal plate is interposed between one fuel battery cell 33 and the other fuel battery cell 33, and one fuel battery cell 33. The cell stack 35 is configured by electrically connecting the support substrate 33a to the oxygen-side electrode 33d of the other fuel cell 33 via the interconnector 33f provided on the support substrate 33a and the current collecting member 43. ing. The current collecting member 43 is configured to spread the fuel battery cell 33, so that the cells can be firmly and electrically connected.

  The support substrate 33a is mainly composed of one or more rare earth element oxides selected from Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr, and Ni or NiO. Is desirable.

The intermediate film 33e formed between the support substrate 33a and the interconnector 33f is mainly composed of ZrO ₂ containing Ni or NiO and a rare earth element. The Ni conversion amount of the Ni compound in the intermediate film 33e is preferably 35 to 80% by volume, more preferably 50 to 70% by volume, based on the total amount. By setting Ni to 35% by volume or more, the conductive path by Ni is increased, the conductivity of the intermediate film 33e is improved, and the voltage drop is reduced. Moreover, by making Ni 80 volume% or less, the thermal expansion coefficient difference between the support substrate 33a and the interconnector 33f can be made small, and generation | occurrence | production of the crack of both interface can be suppressed.

  In addition, the thickness of the intermediate film 33e is preferably 20 μm or less, and more preferably 10 μm or less from the viewpoint that the potential drop is reduced.

The thermal expansion coefficient of the middle rare earth element or heavy rare earth element oxide is smaller than the thermal expansion coefficient of ZrO ₂ containing Y ₂ O ₃ of the solid electrolyte layer 33c, and the thermal expansion of the support substrate 33a as a cermet material with Ni. The coefficient can be made close to the thermal expansion coefficient of the solid electrolyte layer 33c, and cracking of the solid electrolyte layer 33c and separation of the solid electrolyte layer 33c from the fuel side electrode 33b can be suppressed. By using a heavy rare earth element oxide having a small thermal expansion coefficient, the amount of Ni in the support substrate 33a can be increased, and the heavy rare earth element oxide is also used from the viewpoint that the electrical conductivity of the conductive support 33a can be increased. It is desirable.

  Note that the light rare earth elements La, Ce, Pr, and Nd oxides have a rare earth element oxide, a heavy rare earth element, a heavy rare earth element, a heavy rare earth element, a heavy rare earth element, a heavy rare earth element, and a heavy rare earth element. There is no problem even if it is contained in addition to rare earth elements.

  Moreover, the raw material cost can be significantly reduced by using a complex rare earth element oxide containing a plurality of inexpensive rare earth elements in the course of purification. Also in that case, it is desirable that the thermal expansion coefficient of the complex rare earth element oxide is less than the thermal expansion coefficient of the solid electrolyte layer 33c.

  Further, it is desirable to provide a current collecting film 33g made of a P-type semiconductor, for example, a transition metal perovskite oxide, on the surface of the interconnector 33f. When a metal current collecting member is disposed directly on the surface of the interconnector 33f to collect current, the potential drop increases due to non-ohmic contact. In order to make ohmic contact and reduce the potential drop, it is necessary to connect the current collector film 33g made of a P-type semiconductor to the interconnector 33f, and it is desirable to use a transition metal perovskite oxide that is a P-type semiconductor. . The transition metal perovskite oxide is preferably made of at least one of a lanthanum-manganese oxide, a lanthanum-iron oxide, a lanthanum-cobalt oxide, or a composite oxide thereof.

The fuel side electrode 33b provided on the main surface of the support substrate 33a is composed of Ni and ZrO _{2 in} which a rare earth element is dissolved. The thickness of the fuel side electrode 33b is desirably 1 to 30 μm. By setting the thickness of the fuel side electrode 33b to 1 μm or more, a three-layer interface as the fuel side electrode 33b is sufficiently formed. Further, by setting the thickness of the fuel side electrode 33b to 30 μm or less, it is possible to prevent interface peeling due to a difference in thermal expansion from the solid electrolyte layer 33c.

The solid electrolyte layer 33c provided on the main surface of the fuel side electrode 33b is made of a dense ceramic made of partially stabilized or stabilized ZrO ₂ containing 3 to 15 mol% of a rare earth element such as Y. . As the rare earth element, Y or Yb is desirable because it is inexpensive.

  The thickness of the solid electrolyte layer 33c is desirably 10 to 100 μm. Gas permeation can be prevented by setting the thickness of the solid electrolyte layer 33c to 10 μm or more. Moreover, the increase in a resistance component can be suppressed by making the thickness of the solid electrolyte layer 33c into 100 micrometers or less.

The oxygen side electrode 33d is made of a lanthanum-manganese oxide, lanthanum-iron oxide, lanthanum-cobalt oxide of a transition metal perovskite oxide, or at least one porous oxide of a composite oxide thereof. It is composed of conductive ceramics. The oxygen side electrode 33d is preferably a (La, Sr) (Fe, Co) O ₃ system in terms of high electrical conductivity in the middle temperature range of about 800 ° C. The thickness of the oxygen-side electrode 33d is desirably 30 to 100 μm from the viewpoint of current collection.

  The interconnector 33f is a dense body for preventing leakage of fuel gas and oxygen-containing gas inside and outside the support substrate 33a, and the inner and outer surfaces of the interconnector 33f are in contact with the fuel gas and oxygen-containing gas. It has reduction resistance and oxidation resistance.

  The thickness of the interconnector 33f is desirably 30 to 200 μm. By setting the thickness of the interconnector 33f to 30 μm or more, gas permeation can be completely prevented, and by setting it to 200 μm or less, an increase in resistance component can be suppressed.

Between the end of the interconnector 33f and the end of the solid electrolyte layer 33c, for example, a bonding layer made of Ni and ZrO _{2 in} which Y ₂ O ₃ is dissolved is interposed in order to improve the sealing performance. May be.

  The manufacturing method of the fuel cell 33 as described above will be described. First, for example, a rare earth oxide powder and Ni and / or NiO powder are mixed, and a support substrate material in which an organic binder and a solvent are mixed into this mixed powder is extruded and formed into a flat support substrate. A body is prepared and dried and degreased.

Next, Ni and / or NiO powder, ZrO ₂ powder in which a rare earth element is dissolved, an organic binder, and a solvent are mixed to prepare a slurry for the fuel side electrode 33b.

Next, a ZrO ₂ powder with a rare earth element in solid solution, and an organic binder, solvent using a solid electrolyte material obtained by mixing to prepare a sheet-shaped solid electrolyte molded body, a sheet-like solid electrolyte molded body surface, The slurry for the fuel side electrode 33b is applied to form a fuel side electrode molded body on the surface of the solid electrolyte molded body.

  The sheet-shaped solid electrolyte molded body is placed on the support substrate so that the fuel-side electrode molded body is laminated on the support substrate molded body and both ends are spaced apart by flat portions of the support substrate molded body. Wrap around the compact and dry. In addition, you may degrease at this time.

Next, Ni or NiO powder, ZrO ₂ powder in which a rare earth element is dissolved, an organic binder, and a solvent are mixed to prepare a slurry for the intermediate film 33e. This slurry is used as a lanthanum-chromium oxide powder. Then, it is applied to the surface of a sheet-like interconnector molded body formed using an interconnector material in which an organic binder and a solvent are mixed to form an intermediate film molded body on the interconnector molded body.

  The interconnector molded body is laminated on the support substrate molded body exposed from between the ends of the solid electrolyte molded body so that both ends of the interconnector molded body overlap on both ends of the solid electrolyte molded body.

  Thus, the fuel-side electrode molded body and the solid electrolyte molded body are sequentially laminated on one side main surface of the support substrate molded body, and the intermediate film molded body and the interconnector molded body are laminated on the other main surface. A molded body is produced. Each molded body can be produced by sheet molding using a doctor blade, printing, slurry dip, spraying by spraying, or the like, or a combination thereof.

  Next, the multilayer molded body is degreased and cofired at 1300 to 1600 ° C. in an oxygen-containing atmosphere.

  Next, a transition metal perovskite oxide powder, which is a P-type semiconductor, and a solvent are mixed to prepare a paste. The laminate is immersed in this paste, and oxygen is deposited on the surfaces of the solid electrolyte layer 33c and the interconnector 33f. The side electrode molded body and the current collector film molded body are formed by dipping, or directly formed by spray coating and printing. Then, it can bake at 900-1300 degreeC and a fuel battery cell can be produced.

  The fuel cell device of the present invention is made of an inorganic insulating material so that the side surface of one end of the fuel cell 33 in the axial length direction covers the stepped portion c between the interconnector 33f and the solid electrolyte layer 33b. It coat | covers with the coating layer 42 which becomes. The coating layer 42 covers the entire circumferential surface of the fuel battery cell 33. In addition, the coating layer 42 can be formed only on one side surface of the fuel cell in which the interconnector 33f is formed so as to cover the stepped portion c. In this case, the material for forming the coating layer 42 can be reduced, and the coating layer 42 can be easily formed.

  The covering layer 42 is made of a solid electrolyte material or glass. As the solid electrolyte material, the same material as the solid electrolyte layer 33b can be used. Therefore, when the coating layer is made of a solid electrolyte material, the same material as that of the solid electrolyte layer 33b can be used, which facilitates production. On the other hand, glass can be used as the covering layer 42. For example, it is desirable to select a glass having a thermal expansion coefficient intermediate between a seal glass and a fuel cell constituting a cell support plate described later. Thereby, an inclination thermal expansion arrangement | positioning is attained about a fuel cell, a coating layer material, and a seal glass, and generation | occurrence | production of a crack can further be suppressed. The covering layer 42 is desirably formed from an inorganic insulating material having a strength higher than that of the sealing glass. Thereby, even when there is a difference between the thermal expansion coefficients of the members constituting the fuel cell and the seal glass, a coating layer material having a strength higher than the stress caused by the thermal expansion difference is formed at one end of the cell. Thus, the stress generated in the low-strength seal glass can be reduced, and as a result, a crack-free seal glass can be formed.

  As shown in FIGS. 1, 5, and 6, the lower ends of the plurality of fuel battery cell devices configured as described above are supported and fixed to a cell support plate 50 a constituting the top plate of the gas manifold 50, As a result, the lower end portion of the fuel battery cell device is supported and fixed to the gas manifold 50 and is erected. That is, in the state where the plurality of fuel cells 33 are stacked via the current collecting member 43, one end thereof is joined by the sealing glass (solid sealing material) and is supported and fixed to the cell support plate 50a. A cell device is formed, and in this state, the cell support plate 50a is provided as a top plate of the manifold 50, whereby a plurality of fuel cells 33 are erected on the manifold 50. 5 and 6, the illustration of the current collecting member 43 is omitted, and the illustration of the coating layer 42 is omitted in FIG.

  The lower end portion of the coating layer 42 of the fuel cell apparatus is embedded in the seal glass, and the upper portion of the coating layer 42 protrudes from the cell support plate 50a.

  The thickness of the cell support plate 50a is preferably 20 mm or less in view of reducing the weight of the cell support plate 50a, reducing the volume of the fuel cell main body in which a plurality of fuel cells are bundled, and reducing the heat capacity. If it is larger than 20 mm, the weight and volume increase, the heat capacity increases, and the time required for startup becomes longer.

  The reason why the thickness of the cell support plate 50a is 2 mm or more is that if it is thinner than 2 mm, the necessary distance to the seal glass cannot be secured, and the lower end of the fuel cell 33 cannot be firmly joined. is there. The thickness of the cell support plate 50a is preferably 2 mm or more, particularly 5 mm or more from the viewpoint of workability and gas leak yield improvement. In addition, when used as a fuel cell for distributed power generation used for homes and stores of less than 7 kW, in order to reduce the heat capacity and make the heat self-sustained, it is preferably 20 mm or less, particularly 10 mm or less. In this case, the length of the fuel cell is desirably 80 to 300 mm.

  As shown in FIG. 1, the gas manifold 50 is provided with a fuel gas supply pipe 51 for supplying fuel gas into the fuel cell 33.

  The fuel gas supply pipe 51 passes through the inside of the housing and is introduced into the gas manifold 50 from the side surface of the gas manifold 50 via the fuel reformer 55 disposed above the cell stack 35. A gas to be reformed such as city gas or propane gas is supplied to the fuel gas supply pipe 51 from the outside, and is reformed into the gas manifold 50 and the gas passage 34 of the fuel cell 33 via the reformer 55. Fuel gas is supplied.

  The manifold 50 and the fuel gas supply pipe 51 are made of ceramic, metal, or a mixture thereof, but are preferably made of the same material as the support plate 50a.

  The oxygen-containing gas supply pipe 39 extends between the cell stacks 35 to the vicinity of the cell support plate 50a, and supplies an oxygen-containing gas, for example, air from the tip thereof. Excess oxygen-containing gas that has not been used in power generation flows between the cells 33 and flows upward, and is mixed and burned in the vicinity of the cell tip with fuel gas that has passed through the inside of the cells and has not been used for power generation.

  The heat exchanging section 41 is composed of a discharge passage 41a through which combustion gas is discharged and an oxygen-containing gas chamber 41b disposed inside the discharge passage 41a. In other words, the oxygen-containing gas chamber 41b. A discharge passage 41a is disposed around the gas passage, and heat exchange is possible between the combustion gas in the discharge passage 41a and the oxygen-containing gas introduced from the outside.

  In the fuel cell assembly of the present invention, an oxygen-containing gas composed of air is temporarily stored in the oxygen-containing gas chamber 41b, and is supplied between the fuel cells 33 from the oxygen-containing gas chamber 41b via the oxygen-containing gas supply pipe 39. On the other hand, the gas to be reformed such as city gas is supplied to the fuel gas supply pipe 51 and the reformer 55, flows through the gas passage 34 of the fuel cell 33 through the gas manifold 50, and is led out from the cell tip. Combustion with external oxygen-containing gas is performed, and the combustion gas is discharged to the outside through the discharge path 41a.

  In addition, this invention is not limited to the said form, A various change is possible in the range which does not change the summary of invention. For example, in FIG. 3, the fuel side electrode is formed inside the solid electrolyte layer, but the oxygen side electrode can be formed inside the solid electrolyte layer.

  In addition, for example, in the above-described embodiment, the example in which the fuel cell 33 having a plate shape and the plurality of fuel gas passages 34 is used has been described. However, the fuel cell is cylindrical and has one fuel gas passage hole. The shape of the fuel cell is not particularly limited.

  Furthermore, in the above embodiment, an example in which both end portions of the interconnector 33f are overlapped on both end portions of the solid electrolyte layer 33c to form a stepped portion c is described. However, as shown in FIG. In addition, the present invention can be used effectively even when both end portions of the solid electrolyte layer overlap to form a stepped portion.

  The inventor performed a simulation to confirm the effect of the present invention. The simulation was performed by calculating the maximum principal stress caused by the difference in the coefficient of thermal expansion due to the constituent material of the gas manifold in the state where the fuel cell was erected. FIG. 8 is a diagram showing a simulation result of a stress state generated in the seal glass when the fuel cell is erected on the manifold without forming a coating layer on one end portion. From FIG. 8, the stress concentration of the seal glass at the step portion between the solid electrolyte layer and the interconnector was very large, and the maximum principal stress of the seal glass was 159 MPa.

  On the other hand, a crystalline glass is applied to the entire peripheral surface of the lower end portion of the conventional fuel battery cell by dipping 10 mm from the lower surface, dried and fired to form a coating layer having a thickness of 50 μm, A battery cell device was produced. After that, these fuel battery cell devices and current collecting members are alternately stacked, standing in the manifold, and with the coating layer facing down, a seal glass paste is applied so that the thickness of the seal glass after firing is 5 mm. Poured. After drying, a fuel cell assembly was prepared by firing, and a simulation similar to the above was performed. As a result, the maximum principal stress of the seal glass was 113 MPa, and it was found that the stress concentration was alleviated.

Sectional drawing which shows the fuel cell assembly of this invention. Sectional drawing which shows the cell stack of FIG. The cross-sectional perspective view which shows a fuel battery cell. The fuel cell apparatus is shown, (a) is a longitudinal cross-sectional view, (b) is a side view. Sectional drawing which shows the state which stood the fuel battery cell apparatus in the gas manifold. The state which fixed the fuel battery cell apparatus with the sealing glass is shown, (a) is sectional drawing, (b) is partial sectional drawing. The cross-sectional perspective view which shows the fuel cell by which the both ends of a solid electrolyte layer have overlapped on the both ends of an interconnector. Explanatory drawing which shows a simulation result.

Explanation of symbols

33: Fuel cell 33a: Support substrate (support)
33b: Fuel side electrode 33c: Solid electrolyte layer 33d: Oxygen side electrode 33f: Interconnector 34: Gas passage 42: Cover layer 50: Gas manifold 50a: Cell support plate c: Stepped portion

Claims (5)

One end in the axial length direction of the fuel cell, in which a dense solid electrolyte layer and an interconnector surround and surround the side surface of the support body in which the gas passage is formed in the axial length direction. The fuel cell device, wherein the side surface is covered with a coating layer made of an inorganic insulating material so as to cover a stepped portion where the interconnector and the solid electrolyte layer overlap. 2. The fuel cell device according to claim 1, wherein the fuel cell includes a power generation unit in which the solid electrolyte layer is sandwiched between electrode layers and the interconnector on a conductive support. 3. A fuel cell device according to claim 1 or 2, wherein one end of the fuel cell device is joined to a gas manifold by a sealing glass, and the gas passage of the fuel cell device communicates with the gas manifold. Battery assembly. The fuel cell assembly according to claim 3, wherein a part of the coating layer of the fuel cell unit is embedded in the seal glass. The fuel cell assembly according to any one of claims 1 to 4, wherein the coating layer is made of a solid electrolyte material or glass.

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